This invention relates to bilge pumps, and more particularly to bilge pump apparatus having fiber optical conductors and associated transmitters-receivers.
One type of liquid level control for pumping units is known from U.S. Pat. No. 2,424,657 (H. Goodman) in which the operation of a switch depends on an electrically conductive liquid completing an electric circuit to operate a relay for motor operation.
Another type of liquid level control system for a pump motor is known from U.S. Pat. No. 2,975,347 (E. J. Schaefer). This system depends on the fast or slow transmission of heat from a constant source to a bi-metal switch through a shield. The absence of water allows fast conduction of heat through the shield to the switch. The presence of water cools the shield and the transfer of heat is much slower, so that the switch is not activated when water is present.
In U.S. Pat. No. 3,352,246 (Mitsuo Inoue), an automatic submersible pump is operated depending upon the conduction of electricity through water to detect the presence of the water. Conventional tilt type switches to detect water levels is disclosed in U.S. Pat. No. 4,437,811 (Iwata, et al.). The use of electrical or electronic logic means provide the option of running two pumps, interlinked by control means.
The apparatus in U.S. Pat. No. 4,287,427 (Seifres) detects the level of a liquid in a container by modulating the intensity of light through a fiber-optic light guide, a section of which has the cladding removed or partially removed to provide areas where the cladding is thin or absent. Thus the light transmission of the fiber is reduced in the presence of water.
In U.S. Pat. No. 4,950,886 (Claus, et al.), an optical fiber device is disclosed for use in strain measurement by detecting minor changes in laser pulses through microscopic gaps in rigid optical fibers.
Accordingly, the limitations of the prior art in controlling bilge pumps is solved by the improved and novel apparatus of the invention.